Half-Grey Listing
Concepts of http://nolisting.org and greylisting should be known.
Imagine this setup:
example.org IN MX 05 192.0.2.5
example.org IN MX 50 192.0.2.50
example.org IN MX 99 192.0.2.99
All addresses are on the same host running exim.
Exim would go through the whole process (almost)[0] as normal, but will tempreject (almost)[1] everything on 192.0.2.5 and 192.0.2.99.
Is anything wrong about this (WRT to RFCs)?
What might go wrong?
UPDATE 01:
It seems there are a few appliances that can’t properly deal with this setup:
- mgb.ch
- linkedin.com (sending via rightnowtech.com?)
- zuerich.ch (seems to be using a Sophos-Appliance)
- waedenswil.ch (AFAIU they are using a Barracuda-Appliance)
- ticketcorner.ch
I contacted all of them and the feedback I got so far:
- linkedin.com: my request was not about my own account and they told me they can’t do a lot of things I don’t need them to do. They did not seem to even understand the issue, probably due to my request never getting through first level support. There may be more to come yet.
- zuerich.ch: not sure whether they understand the problem but they surely don’t seem to see it as one. So far the reply was "nothing can be done about it".
- waedenswil.ch: Well, the appliance does it that way, so it’s likely correct, was basically their reply. They did promise to look further into it, so I’ll wait and see.
I disabled the setup for now, though, too many broken sites out there …
[0]: since most stuff is rejected anyway, one may want to optimize here
[1]: abuse@ and postmaster@ should probably be unfiltered, just to make sure